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Other Analytes (other + analyte)
Selected AbstractsAnalysis of aromatic and terpenic constituents of pepper extracts by capillary electrochromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 4 2007Alessandro Musenga Abstract An original method based on CEC has been developed for the determination of aromatic and terpenic compounds in extracts of spices obtained from Piper nigrum. The method is based on the use of a fused silica capillary (effective length: 23.5 cm, internal diameter: 100 ,m) packed with a C18 sorbent (packing length: 23 cm, particle size: 5 ,m). The mobile phase is a 50 mM, pH 6.0 ammonium acetate/ACN (10:90 v/v) mixture. Applying a 30 kV voltage, the following 11 compounds were separated and analysed: terpinen-4-ol, caryophyllene oxide, limonene, ,-pinene, 3-carene, ,-pinene, ,-humulene, ,-caryophyllene, ,-phellandrene, eugenol and piperine. Compound determination is carried out using a diode-array detector set at 265 and 338 nm for ,-phellandrene and piperine, respectively, and at 210 nm (reference subtraction at 282 nm) for all the other analytes. The optimised method has been validated with good results in terms of linearity, limits of quantitation, detection and precision. The CEC method was successfully applied to the analysis of essential oils and methanolic extracts of ,black', ,white' and ,green' pepper. [source] Systematic investigation of ion suppression and enhancement effects of fourteen stable-isotope-labeled internal standards by their native analogues using atmospheric-pressure chemical ionization and electrospray ionization and the relevance for multi-analyte liquid chromatographic/mass spectrometric proceduresRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2010Daniela Remane In clinical and forensic toxicology, multi-analyte procedures are very useful to quantify drugs and poisons of different classes in one run. For liquid chromatographic/tandem mass spectrometric (LC/MS/MS) multi-analyte procedures, often only a limited number of stable-isotope-labeled internal standards (SIL-ISs) are available. If an SIL-IS is used for quantification of other analytes, it must be excluded that the co-eluting native analyte influences its ionization. Therefore, the effect of ion suppression and enhancement of fourteen SIL-ISs caused by their native analogues has been studied. It could be shown that the native analyte concentration influenced the extent of ion suppression and enhancement effects leading to more suppression with increasing analyte concentration especially when electrospray ionization (ESI) was used. Using atmospheric-pressure chemical ionization (APCI), methanolic solution showed mainly enhancement effects, whereas no ion suppression and enhancement effect, with one exception, occurred when plasma extracts were used under these conditions. Such differences were not observed using ESI. With ESI, eleven SIL-ISs showed relevant suppression effects, but only one analyte showed suppression effects when APCI was used. The presented study showed that ion suppression and enhancement tests using matrix-based samples of different sources are essential for the selection of ISs, particularly if used for several analytes to avoid incorrect quantification. In conclusion, only SIL-ISs should be selected for which no suppression and enhancement effects can be observed. If not enough ISs are free of ionization interferences, a different ionization technique should be considered. Copyright © 2010 John Wiley & Sons, Ltd. [source] Gold coating of non-conductive membranes before matrix-assisted laser desorption/ionization tandem mass spectrometric analysis prevents charging effectRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 5 2005Alexander Scherl Acquisition of tandem mass spectra from peptides or other analytes deposited on non-conductive membranes is inhibited on instruments combining matrix-assisted laser desorption/ionization with tandem time-of-flight analyzers (MALDI-TOF/TOFÔ) due to a charging effect. A thin layer of gold renders the membrane conductive. This allows adequate data acquisition on MALDI-TOF/TOFÔ systems. Therefore, this methodology extends the capacity of the molecular scanner concept to tandem mass spectrometry. Copyright © 2005 John Wiley & Sons, Ltd. [source] The effect of alkylamine additives on the sensitivity of detection for paclitaxel and docetaxel and analysis in plasma of paclitaxel by liquid chromatography,tandem mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 8 2006Songmei Gao Abstract The formation of multiple molecular ions, especially due to sodium adduct ion formation, is commonly observed in electrospray mass spectrometry and may make reproducible and sensitive quantitation difficult. The objective of this work was to investigate the underlying mechanism involved in the suppression of multiple molecular ion formation and to improve the sensitivity of detection for the two anti-neoplastic agents paclitaxel and docetaxel. The results showed that alkylamine additives could significantly improve the detection of paclitaxel and docetaxel by suppression of multiple molecular ions through preferential formation of a predominant alkylamine adduct ion. Possible binding sites, binding interactions and binding competition were investigated for the sodium adduct and alkylamine adduct ions using various experimental techniques. The formation of a predominant amine adduct ion may be due to increased surface activity in the droplet. The optimal alkylamine for both analytes was octylamine, which increased peak heights of paclitaxel and docetaxel 4.8 and 3.7-fold (n = 3), respectively. The precision of the signals for the analytes was also improved 5.7-fold. A quantitative assay in plasma for paclitaxel was partially validated for the calibration range 1.0,1000 ng/mL (r = 0.9977) when using 0.05% octylamine as a reconstitution solution additive. The limit of detection (LOD) and limit of quantitation (LOQ) were 0.5 and 0.9 ng/mL, respectively. Acceptable precision, accuracy, specificity and sample stability were demonstrated for this assay. This approach may prove useful for other analytes with similar binding sites. Copyright © 2005 John Wiley & Sons, Ltd. [source] Chiral recognition mechanisms with macrocyclic glycopeptide selectors,CHIRALITY, Issue 1 2009Alain Berthod Abstract Macrocyclic glycopeptide selectors are naturally occurring antibiotics produced by microorganisms. They were found to be excellent chiral selectors for a wide range of enantiomers, including amino acids. Four selectors are commercialized as chiral stationary phases (CSP) for chromatography. They are ristocetin, teicoplanin, vancomycin, and the teicoplanin aglycone (TAG). The key docking interaction for amino acid recognition was established to be a charge,charge interaction between the anionic carboxylate group of the amino acid and a cationic amine group of the macrocyclic peptidic selector basket. The carbohydrate units are responsible for secondary interactions. However, they hinder somewhat the charge,charge docking interaction. The TAG selector is more effective for amino acid enantioseparations than the other CSPs. The "sugar" units are however useful allowing for chiral recognitions of other analytes, e.g., ,-blockers, not possible with the aglycone. Thermodynamic studies established that normal phase and reversed phase enantioseparations were enthalpy-driven. With polar waterless mobile phases used in the polar ionic mode, some separations were enthalpy-driven and others were entropy-driven. The linear solvation energy method was tentatively used to gain knowledge about the chiral recognition mechanism. It appeared to be a viable approach with neutral molecules but it failed with ionizable solutes. With molecular solutes and the teicoplanin CSP, the study showed a significant role of the surface charge-induced dipole interaction and steric effects. The remarkable complementary enantioselectivity effect observed with the four CSPs is discussed. Chirality, 2009. © 2008 Wiley-Liss, Inc. [source] | ||||||||||